Recently, on-board chargers for battery operated tools have become desirable. When rechargeable batteries of battery operated tools are being recharged, it is essential that the motor be disengaged or inoperable. The system to be utilized with such on-board charges should prevent the motor from being engaged while the battery is being recharged regardless of the position of the activation switch. For the system to operate effectively, it must be user friendly. If the system for engaging and disengaging the motor circuit is difficult to operate, then operators are likely to attempt to devise a method to by-pass the system, defeating the benefits thereof.
In battery operated tools not having on-board rechargers, preventing activation of the motor when the tool is being recharged has been accomplished by various methods. An example of one approach is in U.S. Pat. No. 3,696,593 to Froud et al., which discloses a receptacle and two plugs which have obstructing members such that the plug corresponding to normal operation of the motor must be removed and a recharging plug must be inserted thereby preventing activation of the motor.
A related approach is disclosed in U.S. Pat. No. 3,581,480 to O'Connor et al., which contains two plugs, one for normal operation of the motor and one for recharging the battery such that to recharge the battery it is first necessary to unplug the first plug thereby preventing activation of the motor.
A more recent approach appears in U.S. Pat. No. 5,085,043 to Hess et al., which discloses an electro-mechanical interlock and module system for lawn mowers or other electrical devices. A mechanical key is adapted to be inserted into a specially configured opening in a top of a motor shroud. The key activates a plunger of a normally open interlock switch, thereby closing the switch and enabling the lawn mower power circuit. An integral tab simultaneously blocks the charging ports so the operator cannot connect a male plug from an outlet--mounted charging transformer while the power circuit is enabled. When the key is removed, the interlock switch returns to an "off" position and the power circuit of the lawn mower is disabled. When the key member is removed, the charging port is exposed permitting connection of the charger circuit to the charging transformer.
The present invention is directed to improving known recharging systems for a battery operated tool having an on-board transformer.